<template>
  <div class="spec-preview" >
    <img :src="defaultImage.imgUrl"  />
    <div class="event" @mousemove="move"></div>
    <div class="big" >
      <img :src="defaultImage.imgUrl" ref="bigImg" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: ["imageList"],
  data() {
    return {
      defaultIndex: 0,
    };
  },
  beforeMount() {
    this.$bus.$on("changeDefault", this.changeDefault);
  },
  methods: {
    changeDefault(index) {
      this.defaultIndex = index;
    },
    move(e) {
       const bigImg = this.$refs.bigImg
       const mask = this.$refs.mask
       let moveX = e.offsetX
       let moveY = e.offsetY
       let Left = moveX - mask.offsetWidth / 2
       let Top = moveY - mask.offsetHeight / 2
       if(Left < 0) {
         Left = 0
       }else if(Left > mask.offsetWidth) {
         Left = mask.offsetWidth
       } 
       if(Top < 0) {
         Top = 0
       }else if(Top > mask.offsetHeight) {
         Top = mask.offsetHeight
       }
       mask.style.left = Left + 'px'
       mask.style.top = Top + 'px'
       bigImg.style.left = -2 *Left + 'px'
       bigImg.style.top = -2*Top + 'px'
    }
  },
  computed: {
    defaultImage() {
      return this.imageList[this.defaultIndex] || {}
    }
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>